1. Field of the Invention
The present invention relates to a head drum for a recording and reproducing apparatus, and in particular to a head drum for a recording and reproducing apparatus which is capable of enhancing a reliability of a grounding apparatus which implements an electric connection between an upper drum and a lower drum of a head drum and preventing a noise due to a grounding apparatus during an operation of the head drum.
2. Description of the Background Art
FIG. 1 is a view illustrating the construction of a fixed type head drum for a recording and reproducing apparatus. The construction of the head drum is as follows.
A lower drum is press-fitted onto a lower portion of a center shaft 30, and an upper drum 20 is rotatably engaged at an upper portion of the same by interleaving upper and lower bearings 21a and 21b.
A head drum 22 is installed at the upper drum 20 for recording a signal into a tape and reproducing the signal recorded on the tape, and a rotor 23 is engaged at an upper drum 20 by an engaging screw 24 for rotating the upper drum 20.
A stator 25 is fixed at an upper portion of the center shaft 30 for rotating the rotor 23 by an electric operation with the rotor 23.
In the head drum for a recording and reproducing apparatus, the upper drum 20 is insulated by a lubricant formed on bearing balls(not shown) of the upper and lower bearings 21a and 21b for thereby being electrically separated from the lower drum 10.
Therefore, a head drum grounding apparatus is installed below the stator 25 for an electrical connection of the lower drum 10 and the upper drum 20. The construction of the conventional head drum grounding apparatus will be explained with reference to FIGS. 2 and 3.
FIG. 2 is a cross-sectional view illustrating the portion A of FIG. 1 which illustrates a conventional head drum grounding apparatus, and FIG. 3 is an exploded perspective view illustrating the construction of a conventional head drum grounding apparatus.
As shown therein, the conventional head drum grounding apparatus includes a ring collar 40 and a tip brush 50.
The ring collar 40 includes an insertion hole 41 into which the center shaft 30 is inserted. An engaging hole 42 communicates with the center shaft 30 in a horizontal direction. The ring collar 40 is engaged to the center shaft 30 using the engaging screw 30 via the engaging hole 42.
An installation hole 44 is formed at one side of the ring collar 40 for engaging a tip brush 50 which will be described later.
The tip brush 50 contacts with the upper drum 20 for electrically connecting the upper drum 20 and the lower drum 10. As shown in FIG. 3, there is provided a brush body 51 made of a carbon material, and a ground spring 52 is fixed at a portion of the brush body 51.
The brush body 51 includes a semicircular contact portion 51a and a connection portion 51b at both ends of the brush body 51. On end of the brush body 51, namely, a contact portion 51a contacts with the upper bearing 21a, the other end of the brush body 51, namely, a connection portion 51b is fixed at the ground spring 52.
One end of the ground spring 52 is connected with the connection portion 51b of the brush body 51 using a conductive adherent material 53.
In the thusly constituted head drum grounding apparatus, the tip brush 50 is installed at the installation hole 44 of the ring collar 40, and one end of the tip brush 50, namely, the contact portion 51a of the brush body 51 contacts with the upper bearing 21a by an elastic force of the ground spring 52, and the other end of the tip brush 50, namely, one end of the ground spring 52 contacts with a lower surface of the stator 25.
In this state, the lower surface of the stator 25 is formed of a phenol which is an insulation material for thereby implementing an insulated state with the ground spring 52. Therefore, the ground spring 52 contacts with an inner surface of the installation hole 44 of the ring collar 40 for thereby implementing a grounded state of the upper drum 20.
In other words, the grounding path is as follows: the upper drum 20.fwdarw.the upper bearing 21a.fwdarw.the contact portion 51a of the brush body 51.fwdarw.the ground spring 52.fwdarw.the inner surface of the installation hole 44 of the ring collar 40.fwdarw.the center shaft 30.fwdarw.the lower drum 10. Therefore, a main substrate(not shown) of the recording and reproducing apparatus is grounded via the above-described paths.
In the conventional head drum grounding apparatus, a certain distance is formed between the installation hole 44 and the tip brush 50 so that the tip brush 50 is upwardly and downwardly movable by an elastic force of the ground spring 52 in the installation hole 44 of the ring collar 40. Therefore, in the conventional art, a contact between the ground spring and the inner surface of the installation hole is not obtained due to the above-described distance, so that it is impossible to obtain an accurate grounding of the tip brush.
In addition, since the ratio between the length of the ground spring and the distance between the inner surface of the installation hole and the ground spring is relatively great, the ground spring may be flexed, so that the brush body 51 may be vibrated. A friction noise may occur at a contact portion of an inner wall of the installation hole 44 of the ring collar 40 due to the flexed grounding spring 52.
The conduction adherent material used for fixing the ground spring 52 to the brush body 51 is protruded beyond the outer surface of the brush body 51, so that it is difficult to install the tip brush 50 at the installation hole 44 of the ring collar 40.